Liquid Crystals and Electronic Calculators

such form of matter. Liquid crystals are materials that have properties of both solids and liquids. They exist at a relatively narrow range of temperatures. At temperatures below this range, liquid crystals act like solids. At temperatures above the range, they act like liquids. The behavior of liquid crystals is due to the shape of the molecules of which they are made. We can think of those molecules as looking like cigars or pencils: they tend to be long and thin. They can be arranged within a material in one of three forms. In nematic crystals, the molecules are all parallel to each other but are free to move back and forth with relation to each other. The molecules in smectic crystals are also parallel to each other but they do not move back and forth; they are, however, further arranged in layers that do pass over each other. And the molecules in cholesteric crystals occur in highly structured layers that are set at slightly different angles than the ones above and below them.

The interesting property about liquid crystals is the way they transmit light. Light can pass through a liquid crystal more easily in one direction than in another. If we look at one of the crystals from one direction, we might see all the light passing through it. But from another direction, no light would be visible. The crystal would be dark. The arrangement of molecules in a liquid crystal can be changed by adding energy to the crystal. If we warm the crystal, for example, molecules may change their position with relation to each other. This fact is utilized in new kinds of medical thermometers that change color with temperature. As body heat changes, the molecules in the liquid crystal change, the light they transmit changes, and